Thermoelectrics

1. TITLE OF THE RESEARCH
HEUSLER ALLOYS FOR
THERMOELECTRIC APPLICATIONS

2. INTRODUCTION
 In recent years, with various structural symmetries, a large
number of materials possessing half metallic (HM)
character was identified, which includes perovskites, double
perovskites, transition metal oxides, Heusler alloys (HAs)
etc.
 Among these materials, HAs are well known for more than
a century. German chemist Fredrich Heusler first
discovered full HA Cu2MnAl in 1903.
 Based on the structural composition, they can be classified
as full HAs with structural formula X2YZ, half-HAs with
structural formula XYZ and quaternary HAs having
structura formula XX’YZ, where X, X’ and Y are transition
metals and Z is a main group (sp) element.

3. These materials can easily be altered through chemical
substitutions and structural variants. This tunability makes
them fascinating candidates for the study of and thermoelectric
applications.
First, experimental realization of HM in the Heusler
compound NiMnSb was made by Groot et al.
Though numerous HAs have been reported, these materials
are still in demand because of their various properties
including excellent controllability, simple fabrication and
tunable physical properties.

4.  To investigate the titanium based Heusler alloys for
thermoelectric application using First Principle calculations
via Wien2K Software.
 To grow polycrystalline single-phase titanium based half-
Heusler compounds with and without dopants
 To analyze bulk size, device quality titanium based half
Heusler single crystals grown by Bridgman - Stockbarger
method for thermoelectric applictaion
 The thermoelectric (TE) device will be designed and
fabricated with the best grown high quality crystals and
further steps will be taken for commercialization of the
fabricated device.
OBJECTIVES

5.  The thermoelectricity is a “Green technology” to
generate electricity without any harmful effect.
 It is useful to recycle the waste heat energy from various
industries to electric energy.
 Thermoelectric devices are used in medical, biological
and industrial sectors for the recovery of waste heat
energy and to refresh the polluted environment.
 It is important that enough expertise is created in the
country to grow large size good quality crystals leading
to economic prosperity in the country.
 The availability of high-quality crystals is equal to the
ability to raise the country’s economy.
SCOPE

6. LITERATURE REVIEW
 S. Bhattacharya et al., have studied the Effect of Sb
doping on the thermoelectric properties of Ti-based
half-Heusler compounds, TiNiSn1−xSbx. They
investigated the structural,magnetic and thermal
properties of the materials
 S. Sakurada et al., have studied the Effect of Ti
substitution on the thermoelectric properties of (Zr,
Hf)NiSn half-Heusler compounds . It was found that
the substitution of Ti for (Zr, Hf) reduced the thermal
conductivity significantly to a low value .
 Nazmiye Kervan et al., have been studied A first-
principle study of half-metallic ferrimagnetism in the
Ti2CoGa Heusler compound. The electronic band
structures and density of states of the Ti2CoGa
compound show that the spin-up electrons
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7. RESEARCH PROPOSAL
 Heusler alloys plays a vital role in waste heat energy
harvesting application.
 Synthesize Pristine and doped Titanium based Heusler
alloy with less lattice thermal conductivity.
 Introduce magnetic and non-magnetic dopants, nano
structuring the synthesised compounds to enhance
figure of merit. 𝒁𝑻 =
𝜶𝟐𝝈𝑻
𝒌
where α is the Seebeck
coefficient, σ is the electrical conductivity , T is the
temperature (K) and k is the thermal conductivity .
 Grown crystals can be converted in to modules for
fabricating a device

8.  In our work, the calculations will be done using density
functional theory (DFT) which is implemented in
WIEN2k package.
 The WIEN2k package is a computer program written in
Fortran which performs quantum mechanical
calculations on periodic solids. It uses the full-potential
linearized augmented plane-wave [FPLA-PW] basis set to
solve the Kohn–Sham equation of density functional
theory.
METHODOLOGY
MODELLING:

9.  In order to investigate the
thermoelectric properties of
Titanium , Boltz-Trap code [8-9]
will be used and it is depend on
the data provided by WIEN2k
code.
 This code is useful to estimate
Seebeck coefficient and power
factor under different
temperature range.
 DFT reduces the quantum
mechanical ground state many
electron problem to self
consistent one electron problem
through Kohn Sham equation.

10. NOVELTY
 To investigate titanium
based Heusler alloy for
thermoelectric
applications.
 The computational results
will be validated with
experimental study.
 Fabricate device for
commercial purpose.

11. REFERENCES
[1] caillat T,borshchevsky , properties of single crystalline semiconducting CoSb3 , Appliied physics 1996,
[2] Kimura, Y., & Chai, Y. W. (2015). Ordered structures and thermoelectric properties of MNiSn (M= Ti, Zr, Hf)-based half-Heusler compounds affected by close relationship
with Heusler compounds. Jom, 67, 233-245.
[3] Bhattacharya, S., Pope, A. L., Littleton IV, R. T., Tritt, T. M., Ponnambalam, V., Xia, Y., & Poon, S. J. (2000). Effect of Sb doping on the thermoelectric properties of Ti-based
half-Heusler compounds, TiNiSn 1− x Sb x. Applied Physics Letters, 77(16), 2476-2478.
[4] Kervan, N., & Kervan, S. (2012). A first-principle study of half-metallic ferrimagnetism in the Ti2CoGa Heusler compound. Journal of Magnetism and Magnetic Materials,
324(4), 645-648.
[5 ] J. De Boeck, et al., “Technology and materials issues in semiconductor based magnetoelectronics”, semicond. Sci. Tech. 17 (4) (2002) 342.
[6] S. Sharma and P. Kumar, “Tuning the thermoelectric properties of YNiBi half-Heusler alloy”, Materials Research Express, vol. 5, (2018), 46528.
[7] R. A. de Groot, et al., “New class of materials: Half metallic ferromagnets”, PRL.50 (25), (1983) 2024-2027.
[8] P. Blaha, et al., “WIEN2k , an augmented plane wave plus local orbitals program for calculating crystal properties”, Vienna Univ. Techno., Austria (2001).
[9]G. K. H. Madsen and D. Sing, “BoltzTraP. A code for calculating band-structure dependent quantities”, J Comput. Phys. Commun., vol. 175, (2006). 67-71.
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